FIG. 1 shows a typical single loop negative feedback amplifier as known in the art. Here the output current (io) is sensed (through the secondary (Is,0) of transformer x0) and applied to the input of M1 (through the primary of the transformer (Ip,0)), thereby resulting in the current-to-current transfer. For the voltage-to-current transfer, the intrinsic transconductance (gm1) of device M1 is used. With these two relationships (i.e., gm1 of M1 and turns ratio of x0), input impedance of the amplifier can be set to the desired value. Since there are only two design variables, the design has as drawback a trade-off between the wanted gain and input impedance.